The terms “three dimensional printing”, “3D printing” and “additive manufacturing” are generally applied to technologies or processes through which three dimensional objects are formed by incrementally adding relatively minuscule amounts of material in a controlled manner. Such processes typically involve converting a 3D computer model of an object into a collection of thin cross-sectional “slices” which are then physically produced in sequence, one upon another, to form the object. Each slice represents a planar section but has a small depth in the third dimension. The smaller that depth is made in the slicing process, the more accurate the produced object will be, provided the physical process is capable of the required resolution. The apparatus that carries out the physical process of such additive building is commonly referred to as a three dimensional printer. Common technologies for three dimensional (or 3D) printing include extrusion of melted plastic or other suitably pliable material onto a build surface (fused deposition modeling or fused filament fabrication), photocuring layers of liquid resin to form solid sections on a build surface within a bath of resin (stereolithography), and binding, sintering or melting together particles of a powder on a build surface within a bed of powder (binder jet, selective laser sintering, selective laser melting).
In extrusion 3D printing, a melted plastic, or other material of similar or suitable consistency, is extruded through a nozzle in close proximity to the surface of a build platform. The nozzle is held from the platform's build surface at a distance equaling the slice depth, and is relatively moved parallel to the plane of the surface to trace an image of the slice. Thus, in the case of plastic extrusion, the slice is drawn on the build surface in molten plastic. The plastic is allowed to become firm, the build platform and nozzle are further separated by the thickness of the next slice, and the next slice is likewise drawn upon the first. The process is repeated until the entire object has been built.
In stereolithography, a light source is used to trace or project an image of a slice onto a surface of a photo-curable liquid, whereby the light energy of the image causes a thin layer of liquid to transform into a solid image of the slice. The first slice is formed against the surface of a build platform that then moves the slice away from the light projector by a distance equaling the depth of the next slice. The process is repeated to form a second slice against the surface of the first slice, and so on, until the entire object has been produced.
In selective laser sintering or melting, a high powered laser is used to trace slice images onto a thin layer of powdered raw material spread over a build surface, causing the heated particles to become joined. The build surface is then lowered and another layer of powder is spread over the first, and the process is repeated. Binder jetting likewise uses a bed of powder spread over a build assembly, but instead of heating the powder to join the particles, ink jets apply a binding fluid in the image of each slice.
The above descriptions are simplistic, and as 3D printing has advanced beyond its 1980s origins many technological enhancements have been made for tightly controlling the processes and variables involved, to provide solutions for demanding industrial applications. The resultant industrial machines are highly sophisticated, complex and expensive. More recently, less elaborate devices that operate on the same basic principles have become of interest to hobbyists, product designers, engineers and other consumers. The majority of devices in this class are machines based on plastic extrusion, but several designs have been published or marketed for hobbyist and consumer grade stereolithography systems with laser diodes or digital light processing (DLP) projectors employed as the transformational energy source.